Agilent Technologies 4395A - Page 406

Limit
Line
Concept
As
you can
see in
Figure
A
-18
,
segments
are
distinct
points
that
dene
where
limit
lines
begin
or
end. Limit
lines
span
the
distance
between
segments
and
represent
the
upper
and
lower test
limits
. Figure
A
-18
shows
another
important
aspect
of
limit
lines
.
The
far left
hand side
of a
set
of
limit lines
will
continue
from
the
minimum
sweep
parameter
value
(
st
ar
t )
and the
far right
hand
side of
a
set
of
limit
lines
will
continue
until
the
maximum
sweep
parameter value
( stop
).
A
segment is
placed
at
a
specic
sweep
parameter
value
(a
single
frequency
for
example). The
rst
segment
denes
the
limit
line
value
from
the
minimum
sweep
parameter
value
.
Once
its
sweep
parameter
value
is
entered,
the
upper
and
lower
test
limit
(+5
dB
and 0
5dB
for
example)
need
to
be
supplied.
Dening
a
second
segment
denes
where
the
rst
set
of
limit
lines
ends
.
This process
is
repeated
to
create
dierent
sets
of
limit
lines
,
each
having new
upper and
lower limits
.Up
to
18
segments
can
be
entered.
Limits
can
be
dened
independently
for
the
two
channels
.
The
example
in
Figure
A
-18
shows
a
combination
of
limit
lines
that change
instantly and
gradually
.
Segment
1
is
at
2
MHz
and
has
an
upper
and
lower
limit
of
+5
and 0
5
dB
,
respectively
.
Notice
the
upper
and
lower
limit
lines
start
at
the
st
ar
t
frequency
(1
MHz)
and end
at
segment
1.
Segment
2
is
also
at
2
MHz
with
dierent
upper and
lower limits
of +10
dB and
0
10
dB
,
changing
the
limit
values instantly
.
Segment
3
is
at 3
MHz with
the
same
limit
value
as
segment
2
to
obtain
a
at
limit
lines
.
Segment
4
is
at
4
MHz with
upper
and
lower
limit
values
of
+15
dB
and
0
15
dB
,
changing
the
limit
values
gradually
.
Notice the
upper
and
lower
limit
lines
start
at
the
segment
and
continue
until
the
stop
frequency
(5
MHz).
Note
Limit
lines
cannot
be
cut.
Therefore
,
when
limit
lines
are
needed
partially
along
the
sweep
parameter
axis
,
the
non-limit-testing
portion must
also be
entered.
Set
the
non-limit-testing
portion
by
forcing
the
upper and
lower limit
values
out
of
range
(+500
dB
and
0
500 dB
for example).
Both an
upper limit
and a
lower
limit
(or
delta
limits)
must
be
dened.
If
only
one limit
is required
for a
particular
measurement,
force
the
other
limit
out
of
range (+500
dB or
0 500
dB
for
example).
Turning ON/OFF
Limit Line/Limit
Test
Limit lines and limit testing features are
off unless explicitly turned
on by the user
.After
entering the limit line information, you can turn
on the limit line feature and optionally
the
limit testing features
. Turning these features
off has no eect on the entered limit line
information.
Segments Entering Order Needs Notice
Generally, the segments do not have to be entered in any particular order
. The
analyzer
automatically sorts them and lists them on the display in increasing order of sweep parameter
value.
One exception is when two segments have the same sweep parameter value as described in
Figure A-18. If the same sweep parameter values exist, the analyzer draws the limit lines
according to entered segment order.For example, in Figure A-18, segment 1 should be entered
in advance of segment 2.
A-30 Basic Measurement Theory